1. Field of the invention
The present invention relates to hydro-pneumatic pressure vessels, and more particularly to a device for maintaining the gas separate from the liquid in the system.
2. Description of the Prior Art
In a typical closed water heating or cooling system, it is customary to maintain the water under pressure and to provide for the expansion of the water by including an expansion tank in the system whereby air under pressure is utilized to maintain the water under pressure and to act as a buffer for the expanding water in the closed system. Since the air in the expansion tank tends to dissolve, especially as the temperature and pressure rises, it has been suggested to provide a diaphragm in the expansion tank as described by C. H. Kirk in an article entitled "How to Control Air in Hydronic Systems", published in The Journal of Plumbing, Heating and Air Conditioning in the early 1960s. The diaphragm will prevent the air from being absorbed in the water by keeping the air separate from the water. Such diaphragms, however, are subject to deterioration due to continuous flexing and aging of the diaphragm, and eventually become the weak point in the system.